Instruction Manual

Sound Level Meter Types 2245 – Instruction Manual Page 36 of 110
Chapter 3
Conformance Testing
3.1 Introduction
This chapter contains the information needed to conduct conformance testing
according to the specified standards.
3.2 Microphone, Accessories and Sound Fields
The acoustical frequency response and calibration depends on the sound field, the
microphone, the microphone accessories used and the electrical frequency response.
To improve the quality of the measurement and help the user to measure correctly the
sound level meter compensates for the sound field, the microphone and the
microphone accessories used by automatically changing the electrical frequency
response and calibration.
This means that a calibration of a microphone is valid for both free-field and diffuse-
field and for all the recommended accessories.
This also means that it is very important that parameters on menus reflect the desired
configuration. The important menus are:
 Measurement settings > Input
 Measurement settings > Broadband parameters and
 Measurement settings > Spectrum parameters
3.2.1 For acoustical tests
A Microphone Type 4966 shall be used and selected in Measurement settings > Input
> Microphone.
3.2.2 For electrical tests
The Electrical Substitute for Microphones shall be used.
In Measurement settings > Input the following shall be selected:
 An Unknown microphone in Microphone,
 Free-field in Sound field,
 Disabled in Windscreen detect and
 None in Windscreen type.
In this way, an uncompensated electrical frequency response is ensured.
3.3 Calibration during Pattern evaluation and Periodic tests
For Pattern evaluation tests (type approval) and Periodic tests, the sound level meter
shall be calibrated.
For Periodic tests performed by a test laboratory, it may be inappropriate to add more
temporary calibrations to the customer's Calibration history. If this is the case the
laboratory should create new microphones (one 4966 and one unknown) in System
settings >Advanced settings > Microphones before the tests. After the tests, these
microphones can be deleted. This removes there Calibration history.
3.3.1 Acoustic calibration
The calibration procedure can be found in section 2.4.1.